PROJECT SUMMARY We propose to assess the effect of extreme weather, such as hurricanes, droughts, and intense storms, on risks for exposure to contaminant mixtures in karst water systems. Karst systems are important sources of freshwater for human consumption, but are highly susceptible to contamination from multiple sources. As a result, karst groundwater poses a significant risk for exposure to contaminant mixtures and hence health impacts. Flow in these systems may occur through fractures, conduits, and rock matrix. Because of their unique characteristics, karst systems respond differently to extreme weather conditions than other aquifers. Under storm conditions, high loads of contaminants and sediments enter the subsurface and are transported rapidly and unattenuated through conduits to storage and exposure points. Under dry conditions, sediments are immobile; contaminants are stored in sediments and the rock matrix, and are slowly released over long periods of time, resulting in long-term exposure. Differences in loads, physicochemical properties, mobility, and storage characteristics result in dynamic and heterogeneous distribution of contaminants in karst waters. However, little is known about how extreme weather impacts the dynamic distribution and exposure of contaminant mixtures in karst water and how they may affect health. The proposed work will assess the effect of extreme weather on (1) groundwater hydraulic and geochemical conditions, (2) sediment transport, deposition, and potential interactions with contaminants, and (3) distribution of contaminant mixtures at points of potential exposure. Building on previous findings and existing infrastructure, the project focuses on the karst region of northern Puerto Rico, which is the focal area of PROTECT?s work to study the impact of exposure to multiple Superfund-related contaminants on adverse pregnancy outcomes. The contaminants to be studied are phthalates, pesticides, chlorinated volatile organic compounds, and metals because they are commonly found in Superfund sites in karst regions in Puerto Rico and can adversely affect pregnancy outcomes. The proposed research will apply innovative data analytics techniques to mine, visualize, and extract patterns and facts from data, and utilize those facts to make inferences and build data-based models. The models will be used to describe and predict the effect of extreme weather on the distribution of mixtures at groundwater and tap water potential points of exposure. This work will also assess the role of karst sediments in the fate and transport of contaminants during extreme weather conditions through novel analysis of depth-related properties in sediment deposits from karst caves. Through an integrated multidisciplinary approach, this project will contribute to the development of (i) innovative methods for assessing exposure risks to multiple, superfund-related hazardous substances (Projects 1 & 3) and their association to adverse pregnancy outcomes (Projects 1 & 2); and (ii) optimized technologies for reducing the amount and toxicity of contaminants in karst waters (Projects 2 & 4).